Avermectin compounds are a series of natural products isolated from the fermentation broth of a strain of Streptomyces avermitilis. The series consists of eight compounds, 4 major and 4 minor. The compounds are disclosed in U.S. Pat. No. 4,310,519. Certain derivatives of such compounds are also disclosed such as the 22,23-dihydro derivatives described in U.S. Pat. No. 4,199,569. The 13-deoxy derivatives of avermectin compounds are disclosed in U.S. Pat. Nos. 4,171,314 and 4,173,571. Avermectins with a 4"-amino group are also highly efficaceous in this invention and are disclosed in U.S. Pat. No. 4,427,663. In addition, the 4"-phosphate derivatives of the avermectin compounds with a 13-O-disaccharide group present are included in the instant combination. Such compounds are disclosed in copending U.S. Pat. application Ser. No. 461,843, now U.S. Pat. No. 4,469,682.